Raša Urbas

Impact of structure and yarn colour on UV properties and air permeability of multilayer cotton woven fabrics

The aim of our work was to establish whether very good to excellent UV (ultraviolet) protective properties of fabrics can be obtained through a suitable fabric construction and yarn colour, at the same time ensuring suitable air permeability.  For this purpose, six different fabric structures divided into three groups were employed. The samples were made in blue and red combinations of weft with different sequences and proportions between the upper and lower weave threads. A comparison of different fabric structures and colours was attempted to enable the assessment of the impact of the mentioned parameters on both, UV protective properties and air permeability of fabrics.  The analysis comprised the investigation of physical and permeability properties, as well as the colour measurements on twelve different cotton fabrics.  The research indicated excellent UV protection (>60) in all samples. UV protection depended on their construction and in a sufficiently closed structure, also on the colour of the used yarn. There was no significant difference between the samples in blue and red. In addition to excellent UV protection, four samples (one double-weft and three double fabrics) also demonstrated very high air permeability, which was 3–5 times higher than in the one-layer sample, which demonstrated the best UV protective properties.  The research has shown that fabrics with a very high ultraviolet protective factor value and good air permeability can be made by using a suitable construction and yarn colours that sufficiently absorb UV light; the latter being particularly important for light summer cotton clothes.

Evaluation of the Structure of Monofilament PET Woven Fabrics and Their UV Protection Properties

The importance of protection against ultraviolet radiation (UV) is increasing daily. The dependence of the UV protection level on different clothes is determined by the shape and design of fabrics, and especially by their construction parameters. The fabric structure represents an important factor which is in most cases the only condition for good protection. Other possibilities to ensure good or even excellent protection, mainly by finishing treatments, can be efficient only if the fabric structure is closed enough. To determine the key parameters which contribute to the closeness of the structure and offer suitable UV protection, an analysis of monofilament woven fabric structure was made. Monofilament fabric samples used in the production of high-module screen-printing meshes, which are characterized by the excellent dimension stability of the structure, the properties of which change with varying diameters of the monofilaments and the fabric density, were chosen for this research. A broad spectrum of similar but structurally different fabrics assures referential samples are available for the evaluation of UV protection properties. In all the samples tested, the parameters of transmission and reflection were measured. Moreover, the values of absorption and the ultraviolet protection factor (UPF) were calculated. The values calculated on the basis of a determined mathematical model matched well with the measured values and they can together represent the basis for successful planning of fabrics with suitable UV protection properties.

Influence of co-current spray drying conditions on agglomeration of melamine-formaldehyde microcapsules

ABSTRACT The drying of microcapsules causes agglomeration and oversized agglomerates disturb fiber melt spinning. In this study, three parameters in co-current spray drying were studied and their influence on agglomeration was established with a morphological analysis, granulometric analysis, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). The results showed that the inlet temperature, feed rate, and dry matter content have a significant influence on agglomeration; thus, their optimal combination was determined. In these conditions, the microcapsules were dried and applied in fibers.

The characterization of microcapsules printed by screen printing and coating technology

The graphic industry is one of the first that began to utilize microcapsules, which are nowadays used in various fields of applications such as: medicine, pharmacy, agriculture, construction industry, chemical industry, food industry, biotechnology, cosmetic industry, photography, electronics, textile and printing industry (Boh et al., 1999; Arshady & Boh, 2003; Boh, 2007; Poncelet & Boh, 2008). Microcapsules are tiny spheres that usually consist of two parts: the core and the shell (Gosh, 2000). Microencapsulation enables the core material to reach the “target” areas without getting affected by the surroundings, while the microcapsule microscopic size enables the consumption of the very small active agent quantity (Gosh, 2000; Dubey et al., 2009; McShane & Ritter, 2010; Microtek Laboratories Inc., 2015). One of the simplest and the most frequently used encapsulation method in the graphic industry is “in situ” polymerization, which provides high active agent loadings and smoothly shaped microcapsules with good mechanical properties (Kuković & Knez, 1998; Gosh, 2000; Nelson, 2001; Starešinič, Šumiga & Boh, 2011; Ocepek et al., 2012). Microcapsules used in printing applications can be activated by the use of different mechanisms, which are mainly based on external pressure, abrasion and heat or light activation (Gosh, 2000; Nelson, 2001; Boh & Šumiga, 2008; Sensor Products Inc., 2015). Rastko Milošević1, Nemanja Kašiković1, Tomislav Cigula2, Urška Stanković Elesini3 and Raša Urbas3

Microcapsules in Printing

Transferring knowledge from nature is known for a long time. Microencapsulated particles that imitate different natural properties of plant seeds, bacterial spores, eggs, and shells present one of the biomimetic solutions. Thanks to their small size, they can be incorporated onto and into different substrates, thus enabling and improving their initial mechanical, structural, physical, and other properties. Their use is almost unlimited.

Melamine formaldehyde microcapsules with fragrance core material: Preparation, properties, and end use:

The aim of this research was to prepare and analyze suitable microcapsules for the chosen end use—that is, bow-ties. The produced microcapsules were composed of melamine formaldehyde microcapsules with fragrance oils in the core. Regarding the properties, the surface morphology (studied by Scanning electron microscopy (SEM)), thermal properties (measured by Simultaneous Thermal Analysis [STA]), size and size distribution (by SEM and ImageJ software), and release behavior of the microcapsules were analyzed. The microcapsules were further (in two trials) applied with a screen-printing technique to textile materials which were investigated by microscopy (SEM) and tested for thickness, mass per unit area, and crease recovery angle. Finally, the scented bow-ties were designed and a subjective wear test was performed by the participants. According to the results, the prepared microcapsules were undamaged, with a spherical and smooth surface. An impermeable shell enabled the fragrance to be released simply by rupturing the microcapsules. This property was desired, since a stronger release through the permeable shell could be annoying for the wearer. During wear, the fragrance faded, but by rubbing the surface of the bow-tie and consequently rupturing the microcapsules, the release of the fragrance was initiated again, before or after wear.

Evaluation of the modified braille dots printed with the UV ink-jet technique

In the past Braille has mainly been printed by embossing or screen printing while in the last decade newer technologies like UV ink-jet and 3D printing are taking their place. Printing braille is no longer limited only to the paper or the cardboard but nowadays, prints can be made on almost any printing material (foil, glass, plastic, wood, textiles etc.). New technologies enable precise printing of elements not only in 2D but also in 3D, where later plays an important role the braille field, due to the fact that braille needs to be tactile recognizable.